Current optical lithography techniques are unable to fabricate structures having pitches less than about 80 nm. To continue scaling semiconductor nodes below 80 nm sizes, complementary patterning processes are in development. One approach involves using multiple sequential patterning operations to shrink the pitch and increase pattern density. An alternative method for shrinking pitch and increasing pattern density is directed self-assembly (DSA) of block copolymers (BCPs). BCPs are copolymers having blocks of two or more different polymerized monomers. Under certain thermodynamic conditions, BCPs can self-assemble to into periodic nanoscale structures. In BCP self-assembly, the different blocks microphase-separate into different domains. DSA involves directing the BCP self-assembly by a chemo-epitaxial or grapho-epitaxial scheme. In such a manner, a BCP thin film having a patterned defined by the different domains of the BCP may be formed. Subsequent processing can involve selective removal of a block to develop the BCP thin film.